1. Field of the Invention
The invention relates to a coil arrangement for transcranial magnetic stimulation of the type having several individual coils with respective individual current terminals, the coils being mounted in a support element.
2. Description of the Prior Art
In the article by Tomas Paus, Robert Jech, Christopher J. Thompson, Roch Comeau, Terry Peters and Alan C. Evans entitled "Transcranial Magnetic Stimulation during Positron Emission Tomography: A New Method for Studying Connectivity of the Human Cerebral Cortex," which appeared in The Journal of Neuroscience, May 1, 1997, vol. 17, no. 9, pp. 3178-3184, a method is specified that enables a mapping of neuronal connections in the brain. By means of transcranial magnetic stimulation (TMS), a neural activity is triggered at a limited location of the brain surface whose function is known. A small coil with a figure-8 conductor configuration is placed at the location of interest--e.g., somewhat above the scalp in the region of the frontal eye area--and a sequence of short magnetic pulses with a magnitude of approximately 1.5 Tesla is applied by feeding in current pulses into the coil. Subsequently, the neuronal response of the brain at other locations is acquired using an imaging method, e.g. by positron emission tomography (PET). If the location of stimulation is the region of the frontal eye area, the response to this stimulation is acquired at the primary visual cortex using PET. In this way, findings concerning the spatial and temporal interconnectedness of brain functions (connectivity) can be obtained.
The TMS coil arrangement specified in this article must be positioned at the desired location. If the stimulation location is to be modified, this requires a new positioning by attending personnel. Due to the time-consuming and thus expensive activity which is necessary given a variation of the location of stimulation, the clinical possibilities for using this known arrangement. Moreover, since the field distribution of the magnetic field is predetermined by the geometry of the coil, additional TMS coil arrangements must be provided if a stimulation with other field profiles is to take place. In addition, the method has only limited availability, due to the imaging by means of PET.
In European Application 0 655 261, an apparatus is specified that is applied externally to the surface of the head as a treatment for delaying the falling out of hair and stimulating hair growth. Several generator elements for the production of electromagnetic waves are arranged on a helmet-like or hat-like components. The effective frequency range is between 10 Hz and 100 Hz and the effective intensity range is between 1 Gauss and 100 Gauss (1 Gauss=0.1 mT). The generator elements are connected with a power generator via respective separate lines.
From European Application 0 148 566, a helmet-like head antenna for magnetic resonance examinations is known. The head antenna is formed by at least one radio-frequency coil that is shaped convexly and/or concavely. The head antenna can thereby be adapted closely to the body part to be examined.
Another arrangement of the type described above is known from European Application 0 709 115. Several coils are arranged on a helmet-like support element. The coils themselves can be driven individually.
U.S. Pat. No. 5,284,144 specifies a combination of a hyperthermia apparatus with a magnetic resonance antenna. The temperature of the heated tissue is monitored via the magnetic resonance antenna. With a connected control unit, the hyperthermia apparatus is controlled so that a predetermined temperature is held constant in the tissue.